1. Field of the Invention
The present invention relates to an automatic analyzer for performing qualitative and quantitative analyses of biological samples, such as blood and urine, and more particularly to an automatic analyzer provided with a constant temperature bath for holding reaction cells at a certain temperature.
2. Description of the Related Art
An automatic analyzer capable of performing qualitative and quantitative analyses of target components in samples in a short time with high accuracy is employed in widespread fields, primarily in inspection centers and large-scaled hospitals which are required to analyze a large number of samples in a short time. The principle of such an automatic analyzer resides in utilizing a reagent which reacts with the target component and causes a chemical change, and analyzing a degree of the chemical change by using a photometer or the like.
To maintain the reaction condition between the sample and the reagent constant for an improvement of measurement accuracy, the automatic analyzer generally has a structure that reaction cells are immersed in constant temperature water held at a certain temperature.
The constant temperature water is circulated while being heated by a heater or the like so that the water is kept at a certain temperature (e.g., about 37° C.). In such a system, however, air bubbles may often mix in and circulate with the constant temperature water.
When those air bubbles attach to the surfaces of the reaction cells, they may impede the photometry made by the photometer. To avoid such a trouble, Patent Reference 1: JP,A 10-282108 discloses a method of removing air bubbles through the steps of (1) when water circulating in a constant temperature bath is drained, draining a certain amount of the circulating water instead of draining all of the circulating water, (2) providing a water supply port such that pure water is delivered in a direction to strike against an inner wall of the constant temperature bath, thereby causing the air bubbles in the water to rise to the water surface, and (3) adding a surfactant into the constant temperature bath and rotating a reaction disk, to which reaction cells are mounted, in one direction or in forward and backward directions so as to carry away the air bubbles. Also, Patent Reference 2: JP,U 58-74161 discloses a method of washing away air bubbles attached to the surface of a reaction cell by throttling a flow of water in a constant temperature bath near the reaction cell so as to increase the flow speed of the water in the constant temperature bath.